1. Field of the Invention
The present invention relates to a method of manufacturing a substrate in which a semiconductor layer is provided over an insulating layer therebetween, especially a method of manufacturing an SOI (silicon on insulator) substrate. In addition, the present invention relates to a method of manufacturing a semiconductor device using a substrate over which a semiconductor layer is provided with an insulating layer interposed therebetween.
2. Description of the Related Art
In recent years, an integrated circuit using an SOI (silicon on insulator) substrate in which a thin single crystal semiconductor layer is formed on an insulating surface, instead of a bulk silicon wafer, has been developed. Since parasitic capacitance between a drain of a transistor and a substrate is reduced by using the SOI substrate, the SOI substrate has attracted attentions as one improving performance of semiconductor integrated circuits.
Smart Cut (registered trademark) method is known as one of methods for manufacturing an SOI substrate (for example, see Patent Document 1). An outline of the method of manufacturing an SOI substrate by Smart Cut method is described below. First, hydrogen ions are implanted into a silicon wafer by an ion implantation method to form a microbubble layer at a predetermined depth from the surface. Next, the silicon wafer into which the hydrogen ions are implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. Then, by heat treatment, the microbubble layer serves as a cleavage plane and a part of the silicon wafer into which the hydrogen ions have been implanted is separated in a thin film shape along the microbubble layer. Accordingly, a single crystal silicon film can be formed over the other bonded silicon wafer. Here, Smart Cut method may also be referred to as a hydrogen ion implantation separation method.
A method has also been proposed in which a single crystal silicon layer is formed over a base substrate made of glass by such Smart Cut method. Since glass substrates can have a larger area and are more inexpensive than silicon wafers, the glass substrates are mainly used for manufacturing liquid crystal display devices and the like. By using such a glass substrate as a base substrate, a large-sized inexpensive SOI substrate can be manufactured.
Further, in Patent Document 2, in order to improve crystal quality of a single crystal silicon layer, a method for irradiating a single crystal silicon layer with a laser beam is disclosed.